Maturation of immunoglobulin G avidity after inactive gE deleted bovine herpesvirus type 1 (BHV-1) marker vaccination

Particularly for countries in which the prevalence of infection is high, prevention and control of infectious bovine rhinotracheitis (IBR) can be done by vaccination programs. Recently, marker vaccines have been used in the control and eradication of bovine herpesvirus type 1 (BHV-1) infection. Vaccine protection and virus circulation were estimated by individual serological testing using both gB- and gE-ELISA blocking tests. However, the efficacy of vaccines in terms of avidity maturation for BHV-1 infection has not yet been clarified. A total of 40 animals divided into two groups were vaccinated twice at 6-mo intervals with either commercial or in-house killed gE-deleted marker BHV-1 vaccines, respectively. Immunoglobulin G avidity maturation for BHV-1 was monitored in serum samples collected 1 mo postvaccination and compared between groups. The avidity index (AI) was expressed as a percentage and results were presented as mean AI + SD. The overall data showed that optical density (OD) values in wells with or without urea treatment had obviously increased. In relation to this, geometric means of AIs increased from 71% to 96% after primary and booster vaccinations, respectively. Based on group-specific data, mean AI was calculated to be 68.99 +/- 24.6 after the primary vaccination, and 96.74 +/- 8.3 after the booster vaccination in group I. For group II, the mean AI for primary vaccination was 57.40 +/- 23.9, and it increased to 97 +/- 8.9 after the booster vaccination. The increase in AI for both groups after the second vaccinations was found to be significant (p < 0.001).